Icariin on relaxation effect of corpus cavernosum smooth muscle

NO-cGMP pathway in penile corpus cavernosal smooth muscle plays an importan t role in penile erection. The level of cGMP is regulated by a balance betw een the rate of synthesis by guanylate cyclase and the rate of hydrolytic b reakdown to guanosine 5' monophosphate (GMP) by phosphodiesterase 5(PDE5). Icariin is isolated from natural drug Epimedii herba, it is shown to have t he relaxation effect on corpus cavernosal smooth muscle of rabbit (IC50: 4x 10(-4) mol/L), and the mechanism of the relaxation effect of Icariin on cor pus cavernosum, believed to have the inhibiting effect on PDE5 and activati on of NO-cGMP pathway to enhancing penile erection.